Field of the Invention
The present invention concerns a disc record player, and more particularly it relates to a mechanism for supporting the pickup arm in a linear tracking arm type disc record player designed so that the pickup arm is allowed to make a linear travel along a radial direction of the disc record mounted on the platter of the player.
As an apparatus for reproducing the recorded sounds of a disc record, there is the known device which is called the linear tracking type disc record player designed so that the pickup arm is allowed to make a linear travel radially of the disc record in the same manner as in the case of a cutter head for obtaining the sound groove. In such a record player, in general, a pickup arm is constructed so that its supporting movable frame is supported on a guide rail so as to be able to travel on this guide rail. The pickup arm supporting frame is adapted to be moved on the guide rail from a separate driving mechanism so as to cause a straight-line travel of the pickup arm radially of the disc record. The driving mechanism employs an endless belt or a feed screw.
Japanese Patent Publication Specification Sho 40-2610 discloses an arrangement wherein a pickup arm is supported on a slidable frame which, in turn, is arranged so as to travel on a guide rail which is fixed to brackets. A feed screw which is supported on the brackets is rotated in synchronism with the rotation of the platter to thereby accomplish a straight-line tracking movement of the pickup arm. The above-mentioned Patent Publication also discloses that the driving mechanism uses an endless belt and further shows a synchronising means which is of the type that a motor switch is adapted to be rendered "on" and "off" in accordance with the positional displacement of the pickup arm.
Also, Japanese Patent Publication No. Sho 47-45002 which is based on the U.S. application Ser. No. 755,598 filed on Aug. 27, 1968 now U.S. Pat. No. 3,572,724 discloses an arrangement wherein a slidable frame which supports a pickup arm has four wheels which are adapted to travel on substantially U-shaped parallel rails which are united together at one end. The driving mechanism of this arrangement employs an endless belt which is provided between these rails. A motor for driving the belt is adapted to be controlled by a switch which is actuated in association with the positional displacement of the pickup arm.
Furthermore, Japanese Patent Publication No. Sho 42-18028 discloses an arrangement wherein a slidable frame for supporting a pickup arm has guide wheels engaging two guide bars so as to be moved along the guide bars. The driving of the slidable frame is performed by a cylinder which is parallel with the guide bars and by a driving roller provided on the slidable frame. This cylinder rotates in synchronism with the rotation of the platter. The driving roller is adapted to be tilted in accordance with the positional displacement of the pickup arm.
In general, in order to insure that a slidable frame which supports a pickup arm moves smoothly without any play on a guide rail in a linear tracking type disc record player, not only a precision processing technique of a very high degree is needed, but also an assembling technique of a very high degree of precision is required, the pickup arm supporting mechanism as a whole becoming complicated, and thus the manufacture of the device tends to become quite expensive. Moreover, the respective component parts are required to be arranged so as to produce as little vibration and noise as possible. Especially, in case the arrangement includes a plurality of guide rails, vibrational resonance is developed between such guide rails. This is an important thing but heretofore no sufficient consideration has been paid to this point.